Theoretical study on the electronic structures and optical properties of blue-green and blue phosphorescent iridium(III) complexes with tetraphenylimidodiphosphinate ligand

Abstract

The electronic structures and photophysical properties of five iridium(III) complexes Ir(tfmppy)2(tpip) (1), Ir(dfppy)2(tpip) (2), Ir(afCNppy)2(tpip) (3), Ir(CNpyN3)2(tpip) (4), and Ir(2fphpta)2(tpip) (5) [where tfmppy = 4-trifluoromethylphenylpyridine; dfppy =4,6-difluorophenylpyridine; afCNppy = 6-fluoro-4-octyloxy-5-cyano-phenylpyridine; CNpyN3 = 2-(4-cyano-phenyl)-[1,2,3]-triazole; 2fphpta=2-(2,6-difluoro-phenyl-[1,2,4]-triazol-3-yl)-pyridine; tpip=tetraphenylimido-diphosphinate] have been investigated by using density functional theory (DFT) methods and time-dependent DFT ones, aiming at elucidating the influences of different substituents and cyclometalated ligands on the emission properties and quantum yield. The calculated results revealed that the different substituents in 1-3 have a great influence on the energy levels, in particular highest occupied molecular orbital. Meanwhile, we have also get a further insight into the reason for different phosphorescence quantum yields of the studied complexes. The higher quantum yield (Φ) reported for 1 was found to be closely related to both its smaller S1–T1 splitting energy ( ) and larger transition electric dipole moment ( ) upon the S0 → S1 transition. Complex 5 is expected to be a potential candidate for blue-emitting material with good organic light-emitting diodes performances. We propose that the optical properties of this class of materials can be tuned by the modifications of the cyclometalated ligands. © 2013 Wiley Periodicals, Inc.